• Molecules and Cells
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• 제39권7호
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• pp.524-529
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• 2016

Controlling the production of diverse cell/tissue types is essential for the development of multicellular organisms such as animals and plants. The Arabidopsis thaliana root, which contains distinct cells/tissues along longitudinal and radial axes, has served as an elegant model to investigate how genetic programs and environmental signals interact to produce different cell/tissue types. In the root, a series of asymmetric cell divisions (ACDs) give rise to three ground tissue layers at maturity (endodermis, middle cortex, and cortex). Because the middle cortex is formed by a periclinal (parallel to the axis) ACD of the endodermis around 7 to 14 days post-germination, middle cortex formation is used as a parameter to assess maturation of the root ground tissue. Molecular, genetic, and physiological studies have revealed that the control of the timing and extent of middle cortex formation during root maturation relies on the interaction of plant hormones and transcription factors. In particular, abscisic acid and gibberellin act synergistically to regulate the timing and extent of middle cortex formation, unlike their typical antagonism. The SHORT-ROOT, SCARECROW, SCARECROW-LIKE 3, and DELLA transcription factors, all of which belong to the plant-specific GRAS family, play key roles in the regulation of middle cortex formation. Recently, two additional transcription factors, SEUSS and GA- AND ABA-RESPONSIVE ZINC FINGER, have also been characterized during ground tissue maturation. In this review, we provide a detailed account of the regulatory networks that control the timing and extent of middle cortex formation during post-embryonic root development.

• 대한치과의사협회지
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• 제9권4호
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• pp.157-160
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• 1971

To compare the effects of various pulp capping agents that are usually applied to human pulp tissue, adult dogs were bred for a certain period and each capping agent was applied experimentally to pulp tissue after vital pulpotomy. Histological observations are as follows. 1) In comparison between methods of vital pulpotomy, one and two appointment method, different courses of healing were observed. In one appointment method, the granulation tissue formation at the amputation sur face of pulp tissue had a tendency to be transformed to scar tissue formation. In two appointment method, more transformation than that of one appointment method from scar tissue to dentin matrix formation were observed. 2) Histologic changes that have appeared in pulp tissue are a) fixation at outer layer b) degeneration at middle layer c) hyperemia and round cell infiltration at inner layer 3) With use of formocresol mixed zinc oxide powder in two appointment method complete formation of dentin matrix were observed. 4) Among the methods and aagents described above formocresol mixed zinc oxide powder in two appointment method appeared to be relatively effective.

• Advances in biomechanics and applications
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• 제1권2호
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• pp.95-109
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• 2014

Peri-acetabular bone ingrowth plays a crucial role in long-term stability of press-fit acetabular cups. A poor bone ingrowth often results in increased cup migration, leading to aseptic loosening of the implant. The rate of peri-prosthetic bone formation is also affected by the polar gap that may be introduced during implantation. Applying a mechano-regulatory tissue differentiation algorithm on a two-dimensional plane strain microscale model, representing implant-bone interface, the objectives of the study are to gain an insight into the process of peri-prosthetic tissue differentiation and to investigate its relationship with implant-bone relative displacement and size of the polar gap. Implant-bone relative displacement was found to have a considerable influence on bone healing and peri-acetabular bone ingrowth. An increase in implant-bone relative displacement from $20{\mu}m$ to $100{\mu}m$ resulted in an increase in fibrous tissue formation from 22% to 60% and reduction in bone formation from 70% to 38% within the polar gap. The increase in fibrous tissue formation and subsequent decrease in bone formation leads to weakening of the implant-bone interface strength. In comparison, the effect of polar gap on bone healing and peri-acetabular bone ingrowth was less pronounced. Polar gap up to 5 mm was found to be progressively filled with bone under favourable implant-bone relative displacements of $20{\mu}m$ along tangential and $20{\mu}m$ along normal directions. However, the average Young's modulus of the newly formed tissue layer reduced from 2200 MPa to 1200 MPa with an increase in polar gap from 0.5 mm to 5 mm, suggesting the formation of a low strength tissue for increased polar gap. Based on this study, it may be concluded that a polar gap less than 0.5 mm seems favourable for an increase in strength of the implant-bone interface.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제11권1호
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• pp.101-116
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• 1989

Proplast and Porous Polyethylene which have porous structures as low-modulus polymers have been recently used in maxillofacial plastic and reconstructive surgery. The purpose of this study was to compare the response of adajacent tissue, new bone formation and stability after augmentation by differen methods of subperiosteal graft using proplast and purous polythylene in rabbit mandible. The augmentation procedure was carried out by dividing into two groups, A and B. A group consisted of subperiosteal graft on the cortex, and the other B group was made up only graft following artificial decortication in the mandibular body of rabbit. The experimental animals were sacrificed on the 1st, 2nd, 4th and 8th week after grafting for macroscopic and light microscopic examination. The samples extracted at the 6th postgrafting week were also used for biometric testing and scanning electron microscopic examination. The results obtained from this study were as follows : 1. Macroscopically, infection of graft site, deformation and migration of graft material were not observed in all experimental groups. 2. B group showed more rapid and increased bone formation and the greater stability than A group, and tissue response was similar to each other. 3. In the tissue response, macrophages and cellular infiltrations were observed in Proplast group, but few in PHDPE group. 4. In bone formation of A group, Proplast group showed no bone formation until the 8th week, but PHDPE group showed small quantity of osteoid tissue from the 2nd week and appositional bone growth with new bone formation at the 8th week. 5. In bone formation of B group, both Proplast and PHDPE group showed bone formation, but PHDPE group showed more rapid and larger bone formation. 6. In pattern of bone formation, Proplast group mainly showed appositional bone growth pattern connected with graft site. On the other hand, PHDPE group showed mixed pattern of new bone formation in the pore connective tissue with appositional bone growth from graff site. 7. The maximum mean values of shear stress were serially $111.3gf/mm^{2}$ in PHDPE of B group, $84.8gf/mm^{2}$ in PHDPE of A group, $32.9gf/mm^{2}$ in Proplast B group, and $15.7gf/mm^{2}$ in Proplast of A group. From above results, It was suggested that the capacity of bone formation and stability between bone and graft material were dependent on the pore size and structure of graft material itself, the state of graft site and tissue response.

• 대한치과보철학회지
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• 제29권2호
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• pp.267-284
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• 1991

Since the concept of a direct contact between bone and implants, without interposed soft- tissue layers, was reported by Dr. $Br{\aa}nemark$, there has been increasing necessity for correct under-standing of bone-implant interface and surrounding tissue response. Beside quality of bone, surgical technique, load applied to implants, one must consider implant materials, design and surface characteristics to obtain osseointegration. In this study HA plasma-sprayed implants, TPS implants and $Al_2O_3$ implants were inserted into the alveolar bone of dog and tissue response was observed with radiograph, stereoscope, light microscope, and scanning electron microscope. Results were as follows : 1. There was rapid and active bone formation in the region adjacent to HA plasma-sprayed implants but in the deep supporting bone only slight bone formation was seen. 2. There was considerable lamella bone formation in the region adjacent to TPS implants and the deep supporting bone became more compact. 3. There was some gap and sclerosing bone formation in the adjacent region of $Al_2O_3$ implants, but there was irregular new bone formation in the deep supporting bone. Therefore, it seems that $Al_2O_3$ is not adequate for osseointegrated implants.

• Food Science and Biotechnology
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• 제14권5호
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• pp.572-575
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• 2005

The effects of cooking method, cooking time and various food ingredients on the formation/ inhibition of heterocyclic aromatic amines (HAAs) in pork products were investigated. Three HAAs, 2-amino-3,8-dimethylimidazo [4,5-f] quinoxaline ($MeIQ_x$), 2-amino-3,4,8-trimethylimidazo [4,5-f] quinoxaline ($DiMeIQ_x$) and 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) were measured in pork products using solid-phase extraction and HPLC. Pork patties were boiled, oven-broiled and pan-fried to internal temperatures of 71, 77 and $88^{\circ}C$. Generally, HAA concentrations increased with increasing internal temperature, and HAA formation was greatest with pan-fried. Selected food ingredients (vitamin E, sodium nitrite, sodium tripolyphosphate, sodium ascorbate, Nanking cherry tissue and cherry tissue extract) inhibited HAA formation in pork patties fried at $225^{\circ}C$ for 10 min/side, with the greater inhibition provided by cherry tissue and its methanolic extract.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2002년도 생물공학의 동향 (X)
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• pp.48-50
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• 2002

Cartilage defects are common and painful conditions that affect people of all ages. Although many techniques have developed, none of the current available treatment options is satisfactory. Recent advances in biology and materials science have pushed tissue engineering to the forefront of new cartilage repair techniques. The purpose of this study is to determine effective regeneration method for tissue-engineered cartilage. A serum free medium was developed for cartilage tissue engineering. Chondrocyte passage number was found to influence greatly on cartilage tissue formation in vivo. Injectable, biodegradable polymer matrix was developed for chondrocyte transplantation through injection. Transplantation of chondrocytes mixed with the injectable matrices resulted in the cartilage formation in nude mice's subcutaneous sites and rabbit knees. This study may lead to the development of tissue-engineered cartilage appropriate for clinical applications.

• 치위생과학회지
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• 제16권6호
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• pp.401-408
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• 2016

Periodontal disease is one of the major dental diseases. Currently, various methods are used for healing and successful regeneration of periodontal tissue damaged by periodontal disease. The periodontal ligament and alveolar bone have received considerable interest for use in periodontal tissue regeneration and induction. However, as the functions of the factors required for tooth attachment and key regulatory factors for periodontal tissue regeneration in the cementum have recently been identified, interest in cementum formation and regeneration has increased. Dental cementum forms in the late phase of tooth development because of the reciprocal regulatory interaction between cervical loop epithelial cells and surrounding mesenchymal cells, which is regulated by various gene signaling networks. Many attempts have been made to understand the regulatory factors and cellular and molecular mechanisms associated with new cementum formation. In this paper, we reviewed the study outcomes to date on the regulatory factors that induce cementum formation and regeneration, focusing on understanding the roles and functions of Wnt signaling in the regulation of cementum formation. In addition, we aimed to obtain information on the useful reciprocal regulatory factors that mediate cementum formation and regeneration through a series of molecular mechanisms.

• Journal of Periodontal and Implant Science
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• 제25권2호
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• pp.438-457
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• 1995

The origin of fibroblasts, their proliferative activity and roles in the early stages of periodontal regeneration were investigated in order to better understand the periodontal healing process in furcation defects of the beagle dog after guided tissue regeneration. Newly divided cells were identified and quantitated by immunolocalization of bromodeoxyuridine (BrdU) injected 1 hour prior to sacrificing the animals. The results were as follows :1. During periodontal healing in horizontal furcation defect, three different stages, namely the granulation tissue, connective tissue, and bone formation stages, were identified on the basis of major types of cells and tissue. 2. In the early stages of periodontal regeneration, both the remaining periodontal ligament and alveolar bone compartment were the major sources. 3. The majority of BrdU-labeled fibroblasts were located at the following areas ; 1) the coronal zone of the defect in case of the connective tissue fanned on the root surface. 2) the area within an 400 ${\mu}m$ distance from the remaining bone level in case of the periodontal ligament. 3) the area within an 100 ${\mu}m$ distance from the bone surface in case of areas of active bone formation.4. The highly proliferative fibroblasts adjacent to bone surface played a major role in the formation of osteoblast precursor cells, whereas both paravascular and endosteal cells played a minor role in new bone formation, In conclusion, it was suggested that the fibroblasts in the remaining periodontal ligament and bone will play a major role in periodontal regeneration, whereas both paravascular and endosteal cells will play a minor role in new bone formation.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권6호
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• pp.613-619
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• 2000

The purpose of the present study was to investigate the effect of Bioactive glass on bone regeneration in the experimental mandibular bone defects. Five rabbits, weighing about 2.0kg, were used. Three artificial bone defects, $5{\times}5{\times}5mm$ in size, were made at the inferior border of the mandible. In the experimental group 1, the bone defect was grafted with $Biogran^{(R)}$ and covered with $Bio-Gide^{(R)}$ resorbable membrane. In the experimental group 2, $Biogran^{(R)}$ was grafted only. In the control group, the bone defect was filled with blood clot and was spontaneously healed. The animals were sacrificed at 1, 2, 4, and 8 weeks after the graft. Microscopic examination was performed. Results obtained were as follows: In the control group, the osteoid tissue was observed at week 1 and the bone trabeculi were connected each other and matured at week 2. The lamellar bone formation appeared at week 4, and the amount of bone tissue was increased at week 8. In the experimental group 1, the fibrous tissue was filled between the granules of Bioactive glass and the cartilage formation was found adjacent to the normal bone at week 1. The bone tissue was formed between the granules at week 2, while the amount of bone tissue increased and the lamellar bone formation was observed at week 4. The lamellar bone was increased at week 8. Histologic findings were Similar between the experimental groups 1 and 2, although the amount of Bioactive glass granules lost was increased in the latter. These results suggest that new bone formation is found around the Bioactive glass granules grafted into the bone defects, and the membrane plays a role in keeping the granules and preventing the fibrous tissue invasion.